In case of inherited property, you have to put in market value at the time of transfer to you, not original purchase price. There is inheritance field in wealth statement for inflows, you put the inherited property market value there, and declare the same amount with the property.
From Income Tax Ordinance:
37. Capital gains
(4A) Where the capital asset becomes the property of the person —
(a) under a gift [from a relative as defined in sub section (5) of section 85], bequest or will;
(b) by succession, inheritance or devolution;
(c) a distribution of assets on dissolution of an association of persons; or
(d) on distribution of assets on liquidation of a company,
the fair market value of the asset, on the date of its transfer or acquisition by the person shall be treated to be the cost of the asset.
EDIT: Just want to add that since you have already declared property, keep it as it is, since there is no tax on inheritance, FBR won't bother with it. The only problem you will face is higher capital gains tax if you sell the property within 8 years after acquiring it.